1. Technical Field
The invention relates to the field of pressure sensors and more particularly to a passive system measuring pressure using radar technology.
2. Background Art
Radar systems and the like use the reflective properties of objects to gather information from a distance. Pressure is not something that radar can detect on its own. A pressure sensor is needed to aid radar in reading pressure. See FIG. 12.
The pressure sensor of the present invention differs from known prior art in that the present pressure sensor is a passive system measuring reflectivity of an RF or electromagnetic (EM) signal, and not just being put into an active system.
For example, U.S. Pat. No. 6,919,521 to Brian L. Miller et al. discloses a pressure sensor that could be made, but fails to teach measuring pressure with an effective dielectric change causing a resonant frequency change. The '521 patent discloses changing the distance between the ground plane and the resonator, or volumetric changes, but does not actually suggest a mechanism for either changing the effective dielectric constant of the resonator or changing the distance between a permanent magnet and the resonator. Unlike the '521 patent disclosure, the present invention uses a membrane to compact a high dielectric material down so that the effective constant rises which shifts the resonant frequency. The '521 patent disclosure also teaches a dielectric filler material being used to measure changes in capacitance, but not resonant frequency shifting. When resonant frequency shifting is mentioned, the '521 patent disclosure links resonant frequency shifting with volumetric changes and proximity with the ground plane changes. Also the '521 patent fails to specify how to measure the resonant frequency shift.
Also, US Published Patent Application No. 2004/0159158 A1 by Ian J. Forster (Forster) is a capacitive pressure sensor. The Forster device uses a foam dielectric to measure capacitance change and outlines attaching it to a system for measuring capacitance. An antenna is disclosed as being part of the capacitor, and further teaches that the foam could disrupt the antenna.
While the above cited references introduce and disclose a number of noteworthy advances and technological improvements within the art, none completely fulfills the specific objectives achieved by this invention.